diff --git a/kong/pdk/service/response.lua b/kong/pdk/service/response.lua
index 7a0598a368ca..7a47419f96fb 100644
--- a/kong/pdk/service/response.lua
+++ b/kong/pdk/service/response.lua
@@ -6,12 +6,12 @@
 local cjson = require "cjson.safe".new()
 local multipart = require "multipart"
 local phase_checker = require "kong.pdk.private.phases"
+local string_tools = require "kong.tools.string"
 
 
 local ngx = ngx
 local sub = string.sub
 local fmt = string.format
-local gsub = string.gsub
 local find = string.find
 local type = type
 local error = error
@@ -26,6 +26,10 @@ local check_phase = phase_checker.check
 cjson.decode_array_with_array_mt(true)
 
 
+local replace_dashes       = string_tools.replace_dashes
+local replace_dashes_lower = string_tools.replace_dashes_lower
+
+
 local PHASES = phase_checker.phases
 
 
@@ -45,7 +49,7 @@ do
   local resp_headers_mt = {
     __index = function(t, name)
       if type(name) == "string" then
-        local var = fmt("upstream_http_%s", gsub(lower(name), "-", "_"))
+        local var = fmt("upstream_http_%s", replace_dashes_lower(name))
         if not ngx.var[var] then
           return nil
         end
@@ -94,7 +98,7 @@ do
         return response_headers[name]
       end
 
-      name = gsub(name, "-", "_")
+      name = replace_dashes(name)
 
       if response_headers[name] then
         return response_headers[name]
@@ -106,7 +110,7 @@ do
           return nil
         end
 
-        n = gsub(lower(n), "-", "_")
+        n = replace_dashes_lower(n)
         if n == name then
           return v
         end
diff --git a/kong/pdk/vault.lua b/kong/pdk/vault.lua
index 08f3a0d03a1c..99e975f6e3f0 100644
--- a/kong/pdk/vault.lua
+++ b/kong/pdk/vault.lua
@@ -17,11 +17,13 @@ local isempty = require "table.isempty"
 local buffer = require "string.buffer"
 local clone = require "table.clone"
 local utils = require "kong.tools.utils"
+local string_tools = require "kong.tools.string"
 local cjson = require("cjson.safe").new()
 
 
 local yield = utils.yield
 local get_updated_now_ms = utils.get_updated_now_ms
+local replace_dashes = string_tools.replace_dashes
 
 
 local ngx = ngx
@@ -30,7 +32,6 @@ local max = math.max
 local fmt = string.format
 local sub = string.sub
 local byte = string.byte
-local gsub = string.gsub
 local type = type
 local sort = table.sort
 local pcall = pcall
@@ -539,7 +540,7 @@ local function new(self)
       base_config = {}
       if self and self.configuration then
         local configuration = self.configuration
-        local env_name = gsub(name, "-", "_")
+        local env_name = replace_dashes(name)
         local _, err, schema = get_vault_strategy_and_schema(name)
         if not schema then
           return nil, err
@@ -553,7 +554,7 @@ local function new(self)
           -- then you would configure it with KONG_VAULT_MY_VAULT_<setting>
           -- or in kong.conf, where it would be called
           -- "vault_my_vault_<setting>".
-          local n = lower(fmt("vault_%s_%s", env_name, gsub(k, "-", "_")))
+          local n = lower(fmt("vault_%s_%s", env_name, replace_dashes(k)))
           local v = configuration[n]
           v = arguments.infer_value(v, f)
           -- TODO: should we be more visible with validation errors?